This is a proposal to continue a research program in which the primary goal is to extend our understanding of the role of psychosocial factors in susceptibility to infectious disease. The major focus of the proposed study is to evaluate the roles of social networks 1 interactions, and interpersonal conflicts and strains in susceptibility to upper respiratory infections. It also attempts to identify causal pathways (psychological, health practice and biological) linking these factors to disease susceptibility. Before being exposed to an upper respiratory virus, 320 volunteers are administered a range of measures to assess social characteristics thought to contribute to or result from social network integration (e.g., social network structure, quantity and quality of day-to-day interactions, interpersonal dispositions, chronic social strains) as well as measures of pathways thought to link social integration to disease susceptibility. Psychological characteristics assessed as possible links between social integration factors and host susceptibility include self-esteem, personal control, and positive and negative affect. Health practices include smoking, alcohol consumption, sleep, diet, and exercise; and endocrine measures include basal levels of epinephrine (epi), norepinephrine (norepi) and cortisol, and the shape of the diurnal cortisol rhythm. Assessment procedures include semi-structured interviews (social support, stress, self- esteem), questionnaires (social networks, control, self-esteem, personality, health practices), a 14-day daily diary (social interactions, affect, health practices), three 24-hour urines (epi and norepi), and 3 days of repeated collection of saliva samples (cortisol). After the psychological, biological, and behavioral assessment procedures are completed, subjects are exposed by nasal drops to one of two rhinoviruses, quarantined and monitored for infection and symptoms for five days. We collect symptom interviews, nasal washings for detection of viral shedding, and objective measures of pathophysiology (temperature, mucus weights, nasal clearance, nasal congestion, presence of inflammatory mediators) before viral-challenge and on each of the 5 days after challenge. Analyses focus on whether interpersonal factors predict clinical illness (virus shedding or four-fold increase in viral- specific antibody plus clinical diagnosis) and whether these relations are explicable in terms of the psychological, endocrine, and health practice mediation.